1. Field of the Invention
This invention relates to a process of producing polyamines from polynitriles using a hydrogenation catalyst in pellet form whereby said pellets are protected from disintegration.
2. Description of the Prior Art
It has been found that some hydrogenation catalysts in pelleted form when used in the hydrogenation of nitriles to corresponding amines tend to disintegrate. During the hydrogenation reaction the catalyst pellets are swollen or disintegrate into fine particles or both phenomenon occur. Due to loss of physical integrity, usefulness of catalyst pellets suffers somewhat in terms of proper control, particularly in a continuous process where such variables as space velocity, etc. must be carefully considered and controlled. Specifically, channeling occurs in the catalyst bed, so there is improper contact of nitrile with catalyst. Also fine particles sometimes plug the reactor or reactor lines.
In U.S. Pat. No. 3,384,666 a method of inhibiting catalyst pellet disintegration is set out. Essentially this method involves use of a sodium, lithium or potassium hydroxide or alkoxide base. While such expedient use of caustic stabilizer has been found efficacious nevertheless we have subsequently discovered certain drawbacks emanating from such use. For example, it has been found that such a process to be efficiently worked must involve neutralizing the caustic and filtering off the salt. This, of course, involves a time consuming, and relatively expensive additional step. In addition, we have particularly discovered here that the caustic reacts with those nitriles which additionally contain an oxy group in a manner such that the desired amine is not obtained. That is, undesirable side reactions occur. We have therefore discovered an improved process of maintaining hydrogenation catalyst pellet integrity of the cobalt-copper-chromium catalyst type without resort to caustic materials.